The Norwegian Mother and Child Cohort Study (MoBa) is an ongoing prebirth cohort study. Enrollment was completed in 2008 resulting in 106,980 pregnancies in the study. The study is based on questionnaires completed by the mother and father, and biological specimens are collected from the mother, father and child. The main purpose of the study is to find causes of diseases. NIEHS is providing partial support for the study, and in 2002 expanded the data collection protocol to include collection of more biologic specimens from the mothers during the 17th week of pregnancy (additional serum, a specimen of whole blood collected in a trace-element free container, and urine). These specimens will enhance the ability to examine the relation of environmental exposures in relation to various health outcomes in the children and their mothers. As of April 30, 2009, 77,104 subjects had provided blood and urine that was collected in conjunction with NIEHS. We added to the MoBa protocol the collection additional urine specimens in pregnancy, at weeks 23 and 29, for a subset of women. 690 women have a complete set of three urine specimens from pregnancy. We previously published a report about how the preservative used in the collection of the urine specimens contaminated them with free bisphenol A, and also makes the specimens difficult to analyze for other analytes such as organophosphate pesticide metabolites. This information has been useful to us in planning studies. Future studies seeking to quantitate bisphenol A will need to measure total and free BPA, so that conjuated BPA can be estimated. This year, in collaboration with Dr. Stephanie Engel at UNC, we conducted pilot studies and determined that the specimens can be analyzed for organophosphate pesticide metabolites and phthalates, and we are now collaborating with her on full studies of these agents in relation to attention-deficit hyperactivity disorder in MoBa children. We also were successful in using the urines in a study of the reliability of phenolic compounds such as parabens during pregnancy, which was published this year (Guidry et al.). We also have studied the maternal plasma concentration of perfluoralkyl substances (PFAS) in relation to various outcomes among women in the MoBa cohort. This year we published one paper on the reliability of the plasma levels over a period of several years (Papadopoulou et al.), and made progress on ongoing studies on PFAS exposure in relation to child growth, and in relation to infections in childhood. Because of our interest in perfluoroalkyl substances, we have also been collaborating on studies of the pharmacokinetics of these compounds, which provide insight into epidemiologic findings. Our publications this year by Wu et al. and Verner et al. were related to the pharmacokinetic subproject. Scientists at NIEHS have developed several studies that are nested within MoBa. A list of the studies currently ongoing includes: Risk factors for cerebral palsy, Determinants of DNA methylation in cord blood, and additional studies on perfluorinated compound exposure and various aspects of health.